WASHINGTON—The Republican-led House Oversight Committee on Thursday requested interviews with former President Joe Biden’s physician and several top aides as it reopened a probe into what was known about Biden’s health and age-related decline while in office.

While House Republicans and Trump appear to be aligned in their desire to investigate Biden’s fitness to serve, there is some frustration brewing among congressional committees about how quickly the Trump administration is responding to some of their requests, according to multiple GOP congressional sources familiar with the matter.

The cover-up of President Biden’s obvious mental decline is a historic scandal,' says one Republican congressman.